[PATCH 5.10 314/406] io_uring: always lock in io_apoll_task_func

Greg Kroah-Hartman
2023-09-17T19:39:40Z

From: Pavel Begunkov <asml.silence@gmail.com>

From: Dylan Yudaken <dylany@meta.com>

[ upstream commit c06c6c5d276707e04cedbcc55625e984922118aa ]

This is required for the failure case (io_req_complete_failed) and is
missing.

The alternative would be to only lock in the failure path, however all of
the non-error paths in io_poll_check_events that do not do not return
IOU_POLL_NO_ACTION end up locking anyway. The only extraneous lock would
be for the multishot poll overflowing the CQE ring, however multishot poll
would probably benefit from being locked as it will allow completions to
be batched.

So it seems reasonable to lock always.

Signed-off-by: Dylan Yudaken <dylany@meta.com>
Link: https://lore.kernel.org/r/20221124093559.3780686-3-dylany@meta.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
io_uring/io_uring.c | 1 +
1 file changed, 1 insertion(+)

--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -5571,6 +5571,7 @@ static void io_apoll_task_func(struct io
if (ret > 0)
return;

+ io_tw_lock(req->ctx, locked);
io_poll_remove_entries(req);
spin_lock(&ctx->completion_lock);
hash_del(&req->hash_node);